Flux shield for an inductor-alternator machine

Abstract

A homopolar inductor-alternator machine is constructed to have lower transient rectances by the incorporation of a current conducting ring concentric with the axis of the rotor and positioned on the rotor and/or the stator. The conducting ring helps prevent time varying fluxes from inducing eddy current flow in the high permeability rotor steel and unlaminated stator flux return path (back iron). The conducting ring acts upon the transient fluxes which occur in the DC flux path of the machine.

What is claimed is: 
     
       1. A homopolar inductor-alternator machine comprising: a rotor,   a stator assembly including two stacks of stator laminations, said stacks having slots on their inner surfaces;   a DC field coil between said two stacks;   an AC winding located in said stator slots and passing below the inner side of said field coil;   a frame of flux conducting material enclosing said field coil, said stator laminations and the AC winding;   means for supporting said rotor in a spaced-apart air gap defining relation with the stator assembly and for permitting rotation of the rotor relative to the stator during stator excitation; and   a current conducting ring concentric with the axis of said rotor, said conducting ring having a lower permeability than said rotor and said frame so that the commutating reactance of the homopolar inductor-alternator is reduced during transient conditions.   
     
     
       2. The inductor-alternator machine of claim 1 wherein said current conducting ring comprises: a sheet of conducting material positioned between said field coil and said motor frame forming a single turn coil concentric with the axis of said rotor.   
     
     
       3. The inductor-alternator machine of claim 1 wherein said current conducting ring comprises a plurality of single turn shorted coils between said AC winding and said field coil, said plurality of single turn shorted coils supported by said AC winding and concentric with the axis of said rotor. 
     
     
       4. The inductor-alternator machine of claim 1 wherein said current conducting ring comprises: a plurality of single turn shorted coils concentric with the axis of the rotor and located between the air gap and said AC winding, said conducting rings being supported by said AC winding and positioned between said laminated stacks.   
     
     
       5. The inductor-alternator machine of claim 1 wherein said current conducting ring comprises: a ring on either side of each of said stator stacks and surrounding said stacks; and   axially extending conducting means for connecting the pair of rings on each stator stack to form a cage configuration permitting direct contact between each stack and said frame, said rings and said axially extending conducting means located in slots in the outer surface of said stacks.   
     
     
       6. The inductor-alternator of claim 1 wherein said conducting ring comprises copper. 
     
     
       7. A homopolar inductor-alternator machine comprising: a rotor with poles spaced about and extending radially from a shaft near each end of said shaft;   a stator assembly including two stacks of stator laminations, said stacks having slots on their inner surfaces;   a DC field coil situated between said two stacks;   an AC winding located in said stator slots and passing below the inner side of said field coil;   a frame of flux conducting material enclosing said field coil, said stator laminations and the AC winding;   means for supporting said rotor in a spaced-apart air gap defining relation with the stator assembly and for permitting rotation of the rotor relative to the stator during stator excitation; and   a current conducting ring surrounding said shaft, said ring positioned between said poles and having a lower permeability than said rotor so that the commutating reactance of the homopolar inductor-alternator is reduced during transient conditions.